JP2014167882A - Composition for oxide superconductor, and method for producing oxide superconductive wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve increase in film thickness, increase in the production speed, and reduction in cost in the production of a superconductive wire.SOLUTION: An oxide superconductor is formed by applying a composition for the formation of a REBaCuO type (RE is at least one kind of element selected from the group consisting of Y, Nd, Sm, Gd, Dy, Eu, Er, Yb, Pr, and Ho) oxide superconductor to a substrate, subjecting the substrate after applying to temporary calcination heat treatment to form a precursor of the oxide superconductor, and subjecting the precursor to final calcination heat treatment to form an oxide superconductor. The oxide superconductor comprises as essential components a RE salt of a 3-8C carboxylic acid free of a ketone group as a RE component, a barium trifluoroacetate as a Ba component, one or more kinds of copper salts selected from the group consisting of a copper salt of a 6-16C branched saturated aliphatic carboxylic acid and a copper salt of a 6-16C aliphatic carboxylic acid as a Cu component, and an organic solvent for dissolving the metal salts.

Description

  The present invention relates to a composition for an oxide superconductor based on REBaCuO (RE is at least one element selected from the group consisting of Y, Nd, Sm, Gd, Dy, Eu, Er, Yb, Pr, and Ho). The present invention relates to an oxide superconducting wire and an oxide superconducting wire manufacturing method.

  Oxide superconductors are expected to be applied to superconducting magnets, superconducting cables, power equipment, and the like because their critical temperature (Tc) exceeds the liquid nitrogen temperature, and various studies have been conducted earnestly.

  In order to apply an oxide superconductor to these superconducting magnets, superconducting cables, power equipment, etc., it is necessary to produce a long wire having a high critical current density Jc and a high critical current value Ic. On the other hand, in order to obtain an oxide superconductor as a long tape-shaped wire, it is necessary to form the oxide superconductor on a tape-shaped metal substrate from the viewpoint of strength and flexibility.

  In addition, since the superconducting properties of oxide superconductors vary depending on the crystal orientation, it is necessary to improve the in-plane orientation. That is, when the crystal orientation of the superconductor is not aligned during crystallization, the superconducting current does not flow smoothly, and the critical current density Jc and the critical current value Ic (Ic = Jc × film thickness × width) become low. For this reason, the crystal needs to be epitaxially grown by inheriting the orientation of the intermediate layer serving as a base, and the crystal must be grown with excellent orientation from the substrate to the film surface.

  Therefore, in order to improve the critical current density Jc, the c-axis of the oxide superconductor crystal is oriented in the direction (film thickness direction) perpendicular to the substrate surface, and the a-axis (or b-axis) is the substrate surface. In-plane orientation in a direction parallel to the surface.

  One of the methods for producing an oxide superconductor thin film on a tape-like metal substrate (hereinafter referred to as “substrate”) is a MOD method (organic acid deposition process: Metal Organic Deposition process). In this method, after a metal organic compound solution is applied to a substrate, the metal organic compound is thermally decomposed by heat treatment (pre-baking heat treatment) at, for example, around 500 ° C. Then, the obtained thermal decomposition product (oxide superconducting precursor) is crystallized by further heat treatment (main baking heat treatment) at a higher temperature (for example, around 800 ° C.) to produce an oxide superconductor. Compared with the vapor phase method (evaporation method, sputtering method, pulsed laser deposition method, etc.) that is mainly manufactured in vacuum, this method requires simple manufacturing equipment, and can handle large areas and complex shapes. It has features such as being easy.

  As this MOD method, a TFA-MOD method (Metal Organic Deposition using Trifluoro Acetates) using an organic acid salt containing fluorine as a raw material is known.

  In this TFA-MOD method, a superconductor is produced by a reaction between an amorphous precursor containing fluorine obtained after a pre-baking heat treatment of a coating film and water vapor, but the decomposition rate of fluoride can be controlled by the water vapor partial pressure during the heat treatment. . From this, the crystal growth rate of the superconductor is controlled, and as a result, a superconducting film having excellent in-plane orientation can be produced. In this method, the RE (123) superconductor can be epitaxially grown from the substrate at a relatively low temperature.

As described above, when a tape-shaped oxide superconductor is manufactured by the MOD method, it is indispensable to increase the film thickness for improving the critical current value Ic for practical use. In order to achieve this thickening by the MOD method using TFA salt as a starting material, it is conceivable to improve the wettability of the raw material solution with respect to the substrate. When the coating film thickness per time is increased, the amount of generation of decomposition products HF and CO ₂ gas is increased at the time of pre-baking heat treatment, so that the coating film scatters, resulting in a tape-like shape having high characteristics. It is difficult to produce an oxide superconducting thick film.

  Therefore, in general, a thick oxide superconductor is formed by increasing the thickness of the oxide superconducting precursor by repeating the steps of applying the raw material and pre-baking heat treatment while suppressing the coating thickness per time. The body is being made. However, in the above-described calcination heat treatment method according to the prior art, decomposition of metal organic acid salts including TFA salt is insufficient because the temperature rising rate during the calcination heat treatment that affects the decomposition rate of metal organic acid salt is high. The organic compound tends to remain in the oxide superconducting precursor film obtained by calcination. Therefore, when the temperature rises during the subsequent crystallization heat treatment, the remaining organic compound is rapidly decomposed to generate cracks and pores in the film.

  This tendency becomes prominent when the oxide superconducting precursor film having a multilayer structure is formed by repeating coating and calcining heat treatment to increase the thickness. As a result, when the obtained oxide superconducting precursor thick film is crystallized to obtain a superconductor film, epitaxial growth becomes difficult, it is difficult to obtain a superconductor thick film with excellent in-plane orientation, and critical current density Jc characteristics Becomes the peak. Furthermore, the critical current density Jc characteristic is remarkably lowered by the generation of cracks.

  To solve this problem, for example, in Patent Document 1, by using a salt of keto acid having 4 to 8 carbon atoms as the RE component, the remaining organic chains such as fluoride in the oxide superconducting precursor film are used. A method for reducing the above is disclosed. Thus, the REBaCuO-based oxide superconductor film is uniformly formed at a high speed.

JP 2010-192142 A

  By the way, in the MOD method, as a method of applying a metal organic compound solution to a substrate, a tape-like substrate on which an oxide intermediate layer is formed is immersed in a metal organic compound solution in which an organic acid salt is dissolved in an organic solvent. A so-called dip coating method in which the substrate is pulled up from the metal organic compound solution is known.

  In order to increase the thickness of the oxide superconductor, there is a desire to increase the thickness of the metal organic compound solution that adheres to the substrate during dip coating. That is, using a composition for an oxide superconductor having higher wettability than a metal organic compound solution containing a salt of a keto acid having 4 to 8 carbon atoms as the RE component shown in Patent Document 1, a higher speed is achieved. There is a desire to produce an oxide superconducting wire having a thick oxide superconductor.

  The present invention has been made in view of the above points, and in the production of an oxide superconductor, a composition for an oxide superconductor, an oxide superconducting wire, and an oxide superconductor capable of increasing the thickness, increasing the speed, and reducing the cost. It aims at providing the manufacturing method of an oxide superconducting wire.

  One aspect of the oxide superconductor composition of the present invention is REBaCuO (RE is at least one selected from the group consisting of Y, Nd, Sm, Gd, Dy, Eu, Er, Yb, Pr, and Ho. The above element) a composition for forming an oxide superconductor, which is an RE salt of a carboxylic acid having 3 to 8 carbon atoms not containing a ketone group as an RE component, and barium trifluoroacetate as a Ba component. One or more types of copper salts selected from the group consisting of a copper salt of a branched saturated aliphatic carboxylic acid having 6 to 16 carbon atoms and a copper salt of an alicyclic carboxylic acid having 6 to 16 carbon atoms as a Cu component; The structure which contains the organic solvent which dissolves these metal salt components as an essential component is taken.

  One aspect of the oxide superconducting wire of the present invention is REBaCuO (RE is at least one element selected from the group consisting of Y, Nd, Sm, Gd, Dy, Eu, Er, Yb, Pr, and Ho. ) Oxide superconducting wire having an oxide superconductor, wherein the oxide superconductor is an RE salt of a carboxylic acid having 3 to 8 carbon atoms not containing a ketone group as an RE component, and trifluoroacetic acid as a Ba component One or more types of copper salt selected from the group consisting of a copper salt of a branched saturated aliphatic carboxylic acid having 6 to 16 carbon atoms and a copper salt of an alicyclic carboxylic acid having 6 to 16 carbon atoms as barium and a Cu component, And the structure which contains the organic solvent which dissolves these metal salt components as an essential component is taken.

  One aspect of the method for producing an oxide superconducting wire according to the present invention is the surface of the base material by pulling up the tape-shaped base material from the container in which the solution of the composition for an oxide superconductor having the above-described configuration is accommodated. An application step of applying the solution to the substrate, a calcination heat treatment step of subjecting the applied solution to a calcination baking process to form a precursor of an oxide superconductor on the surface of the substrate, By performing calcination with calcination, the surface of the base material has REBaCuO (RE is at least selected from the group consisting of Y, Nd, Sm, Gd, Dy, Eu, Er, Yb, Pr and Ho. And a main heat treatment step of forming an oxide superconductor of one or more elements).

  According to the present invention, it is possible to realize a thick film, high speed, and low cost in the production of an oxide superconductor.

The figure which shows the outline of the manufacturing method of a tape-form oxide superconducting wire provided with the REBaCuO type | system | group superconducting layer by MOD method.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

REBaCuO (RE is at least one element selected from the group consisting of Y, Nd, Sm, Gd, Dy, Eu, Er, Yb, Pr, and Ho) according to an embodiment of the present invention. The body composition is a composition that becomes a superconductor composed of a complex oxide of RE, Ba, and Cu. For example, the REBa _y Cu ₃ O _z system (RE represents one or more elements selected from Y, Nd, Sm, Eu, Dy, Gd and Ho, and y ≦ 2 and z = 6.2 to 7) A superconductor having a composition of A.). If RE is Y, the composition of the superconductor can be easily controlled.

  The RE component of the composition for an oxide superconductor according to the present embodiment is composed of one or more types of RE salts of carboxylic acids having 3 to 8 carbon atoms that do not contain a ketone group. Here, the RE salt is preferably an RE salt of propionic acid, and is preferably yttrium propionate that does not contain a fluorine atom in the yttrium salt.

When the number of carbon atoms of propionic acid from which the RE salt is derived is smaller than 3, sufficient solubility cannot be obtained, and a uniform oxide superconducting thick film cannot be obtained. On the other hand, when the number of carbon atoms is larger than 8, the amount of CO ₂ gas generated during the pre-baking heat treatment increases, so that the coating film is likely to be scattered and it is difficult to obtain a high-quality oxide superconducting thick film.

The Ba component of the composition for an oxide superconductor according to this embodiment is (CF ₃ COO) ₂ Ba · nH ₂ O (n is 0 or a hydration number that can be taken). It is usually obtained as an anhydride or monohydrate. The use of trifluoroacetate as a precursor compound for oxide superconductors is known in the past, but its advantage is that it does not pass through barium carbonate, which has a high conversion temperature to oxide superconductors. . This effect is most efficiently obtained when the Ba component is trifluoroacetate. If trifluoroacetate is used for the RE component instead of the Ba component, the effect of the present invention cannot be obtained, and if trifluoroacetate is used for the Cu component, the effect of improving the solubility described later cannot be obtained.

The Cu component contained in the composition for an oxide superconductor according to the present embodiment includes a copper salt of a branched saturated aliphatic carboxylic acid having 6 to 16 carbon atoms and an alicyclic carboxylic acid having 6 to 16 carbon atoms. It consists of 1 or more types chosen from the group which consists of a copper salt of an acid. The copper salt is L ² ₂ Cu · pH ₂ O (L ² is a branched saturated aliphatic carboxylic acid residue having 6 to 16 carbon atoms or an alicyclic carboxylic acid residue having 6 to 16 carbon atoms. , P is 0 or a hydration number that can be taken), and is usually obtained as an anhydrate or a 1-2 hydrate. Examples of the branched saturated aliphatic carboxylic acid having 6 to 16 carbon atoms from which the copper salt is derived include 2-ethylhexanoic acid, isononanoic acid, neodecanoic acid, and the like, and the number of carbon atoms from 6 to 16 from which the copper salt is derived. Examples of the derivative of the alicyclic carboxylic acid copper salt include cyclohexanecarboxylic acid, methylcyclohexanecarboxylic acid, and naphthenic acid. Among these carboxylic acids, those derived from natural products such as naphthenic acid may contain components other than the number of carbon atoms defined in the present invention or those having no branched or alicyclic groups as components. In the present invention, commercially available products can be used as they are, regardless of the presence or absence of these components.

  Here, the composition for an oxide superconductor contains Y-propionic acid, Ba-TFA, and Cu-2-ethylhexanoic acid as an RE salt of a carboxylic acid having 3 to 8 carbon atoms that does not contain a ketone group.

  As said copper salt, since the copper salt of synthetic carboxylic acids, such as copper neodecanoate, copper 2-ethylhexanoate, copper isononanoate, becomes stable in terms of performance and quality, it is preferable. Moreover, copper neodecanoate, copper 2-ethylhexanoate, copper isononanoate, and copper naphthenate have good solubility in their own organic solvents, and further, the solubility of the RE salt and barium salt according to the present invention. It is preferable because it also has an effect of improving.

  In the composition for an oxide superconductor according to the present embodiment, the total content of the RE component, Ba component and Cu component is preferably 10 to 60% by weight, more preferably 30 to 50% by weight, The molar concentration (total of the three components) is preferably 0.5 to 2.0 mol / L, more preferably 0.7 to 1.5 mol / L.

  In the oxide superconductor composition of the present invention, the RE component, Ba component, and Cu component have a molar ratio of RE, Ba, and Cu of Y: Ba: Cu = 1: a: 3. It contains so that it may become Ba molar ratio in the range of a <2. In this case, in order to obtain a high critical current density Jc and a critical current value Ic, the Ba molar ratio in the raw material solution is preferably in the range of 1.0 ≦ a ≦ 1.8, more preferably the raw material solution. The Ba molar ratio in the range is 1.3 ≦ a ≦ 1.7.

  Thereby, the segregation of Ba can be suppressed, and as a result, the precipitation of Ba-based impurities at the grain boundaries is suppressed. Therefore, the generation of cracks is suppressed and the electrical connectivity between the crystal grains is improved, and the superconducting film is formed by the MOD method, and the tape-like oxide superconductivity is more uniform and excellent in the superconducting characteristics of the thick film. An oxide superconducting wire having a body can be easily produced.

  Moreover, the organic solvent in the composition for oxide superconductors according to the present embodiment is not particularly limited as long as it dissolves at least the RE component among the above-described RE component, Ba component, and Cu component. Specifically, the organic solvent is arbitrarily selected in order to obtain desired performance such as coating performance, solubility, viscosity, and dissolution stability, and two or more kinds may be used in combination.

  Examples of the organic solvent include alcohol solvents, diol solvents, ester solvents, ether solvents, aliphatic or alicyclic hydrocarbon solvents, aromatic hydrocarbon solvents, hydrocarbon solvents having a cyano group, and halogenated solvents. Aromatic hydrocarbon-based agents, other solvents and the like can be mentioned.

Examples of alcohol solvents include methanol, ethanol, propanol, isopropanol, 1-butanol, isobutanol, 2-butanol, tertiary butanol, pentanol, isopentanol, 2-pentanol, neopentanol, tertiary pentanol, Hexanol, 2-hexanol, heptanol, 2-heptanol, octanol, 2-ethylhexanol, 2-octanol, cyclopentanol, cyclohexanol, cycloheptanol, methylcyclopentanol, methylcyclohexanol, methylcycloheptanol, benzyl alcohol , Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, Examples include ethylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, 2- (N, N-dimethylamino) ethanol, and 3 (N, N-dimethylamino) propanol. .
Examples of the diol solvent include ethylene glycol, propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, isoprene glycol (3-methyl -1,3-butanediol), 1,2-hexanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,2-octanediol, octanediol (2-ethyl-1, 3-hexanediol), 2-butyl-2-ethyl-1,3-propanediol, 2,5-dimethyl-2,5-hexanediol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1, 4-cyclohexanedimethanol etc. are mentioned.
Examples of ketone solvents include acetone, ethyl methyl ketone, methyl isopropyl ketone, methyl butyl ketone, methyl isobutyl ketone, methyl amyl ketone, methyl hexyl ketone, ethyl butyl ketone, diethyl ketone, dipropyl ketone, diisobutyl ketone, methyl amyl ketone, Examples include cyclohexanone and methylcyclohexanone.
Examples of ester solvents include methyl formate, ethyl formate, methyl acetate, ethyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, 2 butyl acetate, 3 butyl acetate, amyl acetate, isoamyl acetate, 3 amyl acetate, and phenyl acetate , Methyl propionate, ethyl propionate, isopropyl propionate, butyl propionate, isobutyl propionate, 2 butyl propionate, 3 butyl propionate, amyl propionate, isoamyl propionate, 3 amyl propionate, phenyl propionate , Methyl 2-ethylhexanoate, ethyl 2-ethylhexanoate, propyl 2-ethylhexanoate, isopropyl 2-ethylhexanoate, butyl 2-ethylhexanoate, methyl lactate, ethyl lactate, methyl methoxypropionate, ethoxypropyl Methyl pionate, ethyl methoxypropionate, ethyl ethoxypropionate, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monopropyl ether acetate, ethylene glycol monoisopropyl ether acetate, ethylene glycol monobutyl ether Acetate, ethylene glycol mono tert-butyl ether acetate, ethylene glycol monoisobutyl ether acetate, ethylene glycol mono tert-butyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monopropyl ether Acetate, propylene glycol monoisopropyl ether acetate, propylene glycol monobutyl ether acetate, propylene glycol mono second butyl ether acetate, propylene glycol mono isobutyl ether acetate, propylene glycol mono tertiary butyl ether acetate, butylene glycol monomethyl ether acetate, butylene glycol monoethyl ether acetate , Butylene glycol monopropyl ether acetate, butylene glycol monoisopropyl ether acetate, butylene glycol monobutyl ether acetate, butylene glycol mono sec-butyl ether acetate, butylene glycol monoisobutyl ether acetate, butylene glycol mono-tert-butyl ether Examples include ether acetate, methyl acetoacetate, ethyl acetoacetate, methyl oxobutanoate, ethyl oxobutanoate, γ-lactone, dimethyl malonate, dimethyl succinate, propylene glycol diacetate, and δ-lactone.
Examples of the ether solvent include tetrahydrofuran, tetrahydropyran, morpholine, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dipropylene glycol dimethyl ether, triethylene glycol dimethyl ether, dibutyl ether, diethyl ether, dioxane and the like.
Aliphatic or alicyclic hydrocarbon solvents include pentane, hexane, cyclohexane, methylcyclohexane, dimethylcyclohexane, ethylcyclohexane, heptane, octane, decalin, solvent naphtha, turpentine oil, D-limonene, pinene, mineral spirit, swazol # 310 (Cosmo Matsuyama Oil Co., Ltd., Solvesso # 100 (Exxon Chemical Co., Ltd.)) and the like.
Examples of the aromatic hydrocarbon solvent include benzene, toluene, ethylbenzene, xylene, mesitylene, diethylbenzene, cumene, isobutylbenzene, cymene, and tetralin.
Examples of the hydrocarbon solvent having a cyano group include acetonitrile, 1-cyanopropane, 1-cyanobutane, 1-cyanohexane, cyanocyclohexane, cyanobenzene, 1,3-dicyanopropane, 1,4-dicyanobutane, 1,6- Examples include dicyanohexane, 1,4-dicyanocyclohexane, 1,4-dicyanobenzene and the like.
Examples of the halogenated aromatic hydrocarbon solvent include carbon tetrachloride, chloroform, trichloroethylene, and methylene chloride.
Examples of other organic solvents include N-methyl-2-pyrrolidone, dimethyl sulfoxide, dimethylformamide, aniline, triethylamine, and pyridine.
As the above-mentioned organic solvent, those having a boiling point of 80 ° C. or more are preferable because they give uniform coating properties. An alcohol solvent is preferable because it has good wettability to various substrates. 1-butanol, isobutanol, 2-butanol, tertiary butanol, pentanol, isopentanol, 2-pentanol, neopentanol, tertiary pentanol, hexanol, 2-hexanol, heptanol, 2-heptanol, octanol Alcohol solvents having 4 to 8 carbon atoms such as 2-ethylhexanol, 2-octanol, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, diethylene glycol monomethyl ether are preferred.

  The content of the organic solvent in the oxide superconductor composition is 25 to 80% by weight. Considering coating property, metal component concentration, and dissolution stability, 40 to 70% by weight is preferable.

  The composition for an oxide superconductor of the present invention further contains a solubilizer having an amino group in order to dissolve the propionate in an organic solvent. Examples of the amino group include tetramethylurea, n-octylamine, propylamine and the like. In particular, tetramethylurea is preferable because it is a high boiling point solvent.

  Moreover, you may contain arbitrary components, such as a leveling agent, a thickener, a stabilizer, surfactant, and a dispersing agent, in an organic solution. In addition, it is preferable that content of these arbitrary components shall be 10 weight% or less in the composition for oxide superconductors of this invention. Specific examples of the optional component include organic acids that function as a leveling agent. As the organic acid, an organic acid having 6 to 30 carbon atoms which may have a hydroxyl group, may have a branch, or may have an unsaturated bond is preferable. Specific examples include 2-ethylhexanoic acid, isononanoic acid, neodecanoic acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, margaric acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, Lignoceric acid, serotic acid, montanic acid, melicic acid, tocic acid, lindelic acid, tuzuic acid, palmitoleic acid, petrothelic acid, oleic acid, elaidic acid, vaccenic acid, linoleic acid, linoleic acid, γ-linolenic acid, linolenic acid Examples include acid, ricinoleic acid, 12-hydroxystearic acid, cyclohexanecarboxylic acid, methylcyclohexanecarboxylic acid, naphthenic acid, rosinic acid, and abietic acid, and abietic acid is preferable.

  In addition, it is preferable that the viscosity of the composition for oxide superconductor bodies of this invention is the range of 2-150 [mPa * s], and is 20 [mPa * s] here.

<Outline of MOD Method Using Composition for Oxide Superconductor According to this Embodiment>
FIG. 1 includes a REBaCuO (RE is at least one element selected from the group consisting of Y, Nd, Sm, Gd, Dy, Eu, Er, Yb, Pr, and Ho) based on the MOD method. The outline of the manufacturing method of a tape-shaped oxide superconducting wire (hereinafter also referred to as “YBCO superconducting wire”) is shown.

First, a Gd ₂ Zr ₂ O ₇ intermediate layer and a Y ₂ O ₃ intermediate layer are sequentially formed on a tape-shaped Ni alloy substrate by an ion beam sputtering method as a template, and an MgO intermediate layer is further formed thereon by an IBAD method. Is deposited. Thereafter, a LaMnO ₃ intermediate layer is formed by a sputtering method and a CeO ₂ intermediate layer is sequentially formed by a PLD method or a sputtering method to form a base material that is a composite substrate.

  Then, on this substrate, in the coating step (a), the composition for oxide superconductor according to the present embodiment, that is, Y-propionate, Ba-TFA salt (trifluoroacetate) and Cu— A mixed solution (superconducting raw material solution) 30 in which ethyl hexane salt is dissolved in an organic solvent at a ratio of Y: Ba: Cu = 1: 1.5: 3 is applied by a dip coating method.

  In the dip coating method, a tape-like base material in which an oxide intermediate layer is formed on a substrate is immersed (immersed) in a container in which the mixed solution 30 is stored, and then pulled up from the mixed solution 30, thereby In this method, a mixed solution is applied to the surface. In the dip coating method, when the film is pulled up, the film thickness is adjusted by the surface tension of the mixed solution, and the mixed solution is applied, that is, a coating film is formed. In the dip coating method, the film thickness can be controlled by the pulling speed of the substrate and the solution concentration. The relationship between the substrate pulling speed and the film thickness applied to the substrate at the time of pulling is such that the lower the pulling speed is, the thinner the film is, and the higher the pulling speed is, the thicker the relationship is. Here, it is desirable that the moving speed of the base material in the dip coating method is in the range of 5 to 30 [m / h].

  Thus, after apply | coating the mixed solution 30, temporary baking is carried out at the temporary baking heat treatment process (b). In the pre-baking heat treatment step (b), for example, the wire 49 applied with the mixed solution 30 (see FIG. 1A) is spirally wound around the peripheral surface of the cylindrical body. The cylindrical body around which the wire 49 is wound in this manner is heated by a heater or the like for a predetermined time in an atmosphere having a predetermined water vapor partial pressure and oxygen partial pressure while rotating in the baking apparatus. This coating step (a) and pre-baking heat treatment step (b) are repeated a predetermined number of times to form a film body as a superconducting precursor having a desired film thickness on the intermediate layer of the substrate. In FIG. 1, the wire rod in the middle of the formation of the film body as the superconducting precursor on the substrate (the state before the application of the mixed solution 30 or the state where the coating film after the pre-baking heat treatment is formed) 49. In the calcining heat treatment step (b), the wire is calcined and heat treated in a temperature range of 400 to 500 ° C. in an atmosphere of a water vapor partial pressure of 3 to 76 Torr and an oxygen partial pressure of 300 to 760 Torr, for example, in a calcining apparatus. It is preferable. Moreover, the temperature increase rate in temporary baking heat processing can be 30 [degree-C / min] or more. The pre-baking heat treatment time is desirably 1 to 10 hours, more preferably 2 to 7 hours.

  Thereafter, for the tape-shaped wire 50 in which the film body as the superconducting precursor is formed on the intermediate layer of the base material, in the main firing heat treatment step (c), crystallization heat treatment of the film body of the superconducting precursor, That is, a heat treatment for generating a YBCO superconductor is performed. In this firing heat treatment step (c), for example, a wire is spirally wound around the circumferential surface of the cylinder, and the atmosphere of a predetermined water vapor partial pressure and oxygen partial pressure is rotated while rotating the cylinder in the firing apparatus. Inside, it is heated by a heater or the like for a predetermined time. In the main baking heat treatment step (c), the main baking heat treatment is preferably performed in a temperature range of 700 to 800 ° C. in an atmosphere of a water vapor partial pressure of 30 to 600 Torr and an oxygen partial pressure of 0.05 to 1 Torr in a baking apparatus. The main heat treatment time is preferably 5 to 30 hours, more preferably 10 to 15 hours while introducing water vapor gas. In this main baking heat treatment, the precursor is heated at a temperature elevation temperature of 30 [° C./min].

  Next, an Ag stabilization layer is formed on the YBCO superconductor by a sputtering method in the stabilization layer forming step (d), and then post-heat treatment is performed in a post-treatment step (e) to form a tape-shaped YBCO superconducting wire ( An oxide superconducting wire) 60 is manufactured.

  Here, the frequency | count of repeating a coating process (a) and a temporary baking heat treatment process (b) is 1 time or more and 10 times or less.

  In the coating step (a), as the mixed solution, REBaCu according to the present embodiment (RE is at least one selected from the group consisting of Y, Nd, Sm, Gd, Dy, Eu, Er, Yb, Pr, and Ho). A composition for an oxide of a kind or more) based oxide superconductor is applied to a substrate (shown as wire 49 in the figure). This composition for an oxide superconductor contains, as an essential component, an RE salt of a carboxylic acid having 3 to 8 carbon atoms that does not contain a ketone group as an RE component.

  Thereby, in the application step (a), in the case of applying the mixed solution to the substrate by the dip coating method, the wettability is improved as compared with the case of applying the mixed solution containing the RE salt containing the ketone group. Can be planned. For example, the RE component in the mixed solution that is the oxide superconductor composition according to this embodiment is a propionate (hereinafter referred to as “propion solution”). When the mixed solution 30 containing this propion liquid is used, the conventional mixed solution containing 2-ethylhexane salt as a mixed solution containing a ketone group (hereinafter referred to as “ethylhexane liquid”) is used. Compared to, it is hard to dry. In other words, when dip-coating with an ethyl hexane solution as the RE component is easier to evaporate (easily fly) than when dip-coating with the propion solution (oxide superconductor composition) of the present embodiment.

For this reason, when the substrate is lifted after coating with ethyl hexane solution, the coating film on the substrate is dried in a shape swollen at both ends as viewed in the axial direction along with factors such as the surface tension and polarity of the mixed solution.
On the other hand, in the present embodiment in which dip coating is performed with a propion solution, since it contains a solubilizing agent having an amino group, it is difficult to evaporate (not easily fly). For this reason, the coating film on the substrate pulled up by applying the propion liquid is dried in a state where both end portions and the central portion are coated as uniform film bodies as viewed in the axial direction.

  Thereby, in comparison with the dip coating with the ethyl hexane solution, the dip coating with the propion solution of the present embodiment increases the film thickness applied at one time. For example, when dip coating is performed with ethyl hexane solution at a solution concentration and pulling speed optimized so that the film thickness applied at one time becomes the maximum thickness, the film thickness applied at one time (application film thickness ) Was 0.11 [μm / coat]. On the other hand, when dip coating is performed with the propion solution (mixed solution 30) of the present embodiment at a solution concentration and a pulling speed optimized so that the film thickness to be applied at one time is maximized, The coating film thickness was 0.3 [μm / coat] or more. Thus, the coating film that becomes the superconducting precursor can be formed with a thicker film than in the case of using ethyl hexane solution.

Moreover, the mixed solution 30 as the composition for an oxide superconductor containing propionic acid (C ₃ H ₆ O ₂ ) salt as an essential component as the RE component is more C than levulinic acid (C ₅ H ₈ O ₃ ). Can be reduced. Thereby, generation | occurrence | production of a carbon dioxide gas is reduced, generation | occurrence | production of a crack can be reduced and the film thickness of an oxide superconductor can be achieved more.

  The Ni alloy substrate may have a biaxial orientation or may have a biaxial orientation intermediate layer formed on a non-oriented metal substrate. Further, the intermediate layer is formed of one layer or a plurality of layers. As an application method, it is possible to use an inkjet method, a spray method, etc. in addition to the dip coating method described above, but basically, this example is applicable as long as it is a process capable of continuously applying a mixed solution onto a composite substrate. Not constrained by. The film thickness to be applied at one time is 0.01 μm to 2.0 μm, preferably 0.1 μm to 1.0 μm.

  The oxide superconductor formed in this way is used for wires, devices, or power equipment such as power cables, transformers, and current limiters.

  EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited to this Example.

<Example 1>
In Example 1, a REBaCu-based oxide superconductor (YBCO superconductor) is formed on a tape-shaped substrate by the MOD method shown in FIG. 1 using the oxide superconductor composition of the present embodiment. did. The base material of Example 1 includes Hastelloy (registered trademark) as a substrate and an intermediate layer formed by sequentially stacking GZO, MgO, LMO, and CeO ₂ on the Hastelloy (registered trademark). Prepare. The mixed solution 30 (see FIG. 1) used in the dip coating method includes Y-propionic acid, Ba-TFA, Cu-2-ethylhexanoic acid not containing fluorine atoms, and these Y-propionic acid, Ba-TFA, Cu. And an organic solvent for dissolving the component of 2-ethylhexanoic acid. In addition, the organic solvent includes a solubilizer having an amino group that dissolves propionic acid (here, tetramethylurea). In the dip coating method, the critical one-time coating film thickness of the superconductor is 1.2 [μm / coat] (application speed 5 [m / h]), and the one-time coating film thickness is 0.49 [μm. / Coat]. This was repeated a plurality of times until a desired film thickness (here, a film thickness exceeding 2.5 [μm]) was obtained.

<Example 2>
When the YBCO superconductor is formed by the MOD method in the same manner as in Example 1, compared with Example 1, the coating speed is doubled to 10 [m / h] in the coating process, and the mixed solution 30 is applied to the substrate. (See FIG. 1) was dip coated to form a YBCO superconductor. In Example 2, the coating film thickness at one time was 0.77 [μm / coat]. This was repeated a plurality of times until a desired film thickness (here, a film thickness exceeding 2.0 [μm]) was obtained.

<Example 3>
In the organic solution of the mixed solution used in Example 1, a mixed solution having a structure not containing a solubilizing agent having an amino group was applied to the same substrate as that of Example 1 by the dip coating method. An oxide superconducting wire was formed by subjecting the coating film thus obtained to temporary baking heat treatment and main baking heat treatment. The coating speed was 5 [m / h], and the other conditions for coating, pre-baking heat treatment, and main-baking heat treatment were the same as in the examples.

<Reference Example 1>
As a reference example, using a mixed solution containing Y-TFA, Ba-TFA, and Cu-2-ethylhexanoic acid as a TFA-MOD raw material solution, a MOD method was applied to a tape-like substrate in the same manner as in Example 1. A YBCO superconductor was formed. The coating speed is 5 [m / h]), and the coating film thickness at one time is 0.11 (about 0.1) [μm / coat], and the desired film thickness is obtained by repeating the coating process and the pre-baking process. (Here, it was repeated 20 times to obtain a film thickness of 2 [μm]). In addition, the conditions in the coating, pre-baking heat treatment, and main baking heat treatment were the same as those in the example.

  These measurement results are shown in Table 1.

  From Table 1, in Examples 1 to 3, the film thickness of the mixed solution applied to the substrate by one dip coating is thicker than that of Reference Example 1. In Example 1, a film thickness that is about four times thicker is formed, and in Example 2, a film thickness that is about seven times thicker than the single-application film thickness of Reference Example 1 is formed. Furthermore, in Example 3, the film thickness about 4 times thicker than the single coating film thickness of the reference example 1 was formed.

In Example 1, in order to obtain the desired film thickness of the YBCO superconductor in the oxide superconducting wire, the coating process and the pre-baking heat treatment process were repeated 6 times to laminate the coating film. In order to obtain the same film thickness as in Example 1 using Reference Example 1, it is necessary to repeat the coating process and the pre-baking heat treatment process in the MOD method 29 times. Therefore, it can be seen that Example 1 achieves a thicker film, higher speed, and lower manufacturing cost compared to Reference Example 1 when forming an oxide superconducting wire having an oxide superconductor. It was. In addition, the critical current value Ic of Example 1 was 791 [A / cm-w], and the critical current density Jc was 2.7 [MA / cm ² ], which showed excellent characteristics. The critical current value Ic and the critical current density Jc (voltage reference 1 μV / cm) showing the superconducting characteristics were measured by a direct current four-terminal method.

  Further, as in Example 2, when the coating speed of the mixed solution 30 (see FIG. 1) in the dip coating method in Example 1 is 5 → 10 [m / h], the coating process and the pre-baking heat treatment process are repeated. The number of times can be further reduced. Thus, in Example 2, when an oxide superconducting wire having an oxide superconductor is formed, a further increase in thickness, speed, and manufacturing cost are achieved as compared with Example 1.

  The embodiment of the present invention has been described above. The above description is an illustration of a preferred embodiment of the present invention, and the scope of the present invention is not limited to this. That is, the description of the configuration of the apparatus and the shape of each part is an example, and it is obvious that various modifications and additions to these examples are possible within the scope of the present invention.

  The composition for an oxide superconductor, the oxide superconducting wire, and the oxide superconducting wire manufacturing method according to the present invention have the effect of increasing the thickness, increasing the manufacturing speed, and reducing the cost. This is useful when manufacturing oxide superconducting wires.

30 Mixed solution 49, 50 Wire 60 YBCO superconducting wire

The present invention relates to a composition for an oxide superconductor based on REBaCuO (RE is at least one element selected from the group consisting of Y, Nd, Sm, Gd, Dy, Eu, Er, Yb, Pr, and Ho). things, a method of manufacturing 及 beauty oxide superconducting wire.

The present invention has been made in view of the foregoing, in the preparation of oxide superconductor thick film, the oxide superconductor composition can be accelerated and cost reduction,及 Beauty oxide superconductor It aims at providing the manufacturing method of a wire.

Oxide superconductor composition according to the present invention, a method of manufacturing 及 beauty oxide superconducting wire, a thick film, has an advantage of being able to increase the speed and cost of manufacture, oxides MOD method This is useful when manufacturing a superconducting wire.

Claims (9)

Composition for forming REBaCuO (RE is at least one element selected from the group consisting of Y, Nd, Sm, Gd, Dy, Eu, Er, Yb, Pr and Ho) based oxide superconductor Because
An RE salt of a carboxylic acid having 3 to 8 carbon atoms not containing a ketone group as an RE component;
Barium trifluoroacetate as a Ba component,
One or more types of copper salts selected from the group consisting of copper salts of branched saturated aliphatic carboxylic acids having 6 to 16 carbon atoms and copper salts of alicyclic carboxylic acids having 6 to 16 carbon atoms as the Cu component;
An organic solvent for dissolving these metal salt components,
As an essential component,
Composition for oxide superconductor. The RE component comprises an yttrium salt;
The composition for an oxide superconductor according to claim 1. The RE component comprises a propionate containing no fluorine atom,
The composition for oxide superconductors according to claim 1 or 2. The organic solvent includes a solubilizer having an amino group,
The composition for oxide superconductors according to any one of claims 1 to 3. An oxide superconducting wire having a REBaCuO (RE is at least one element selected from the group consisting of Y, Nd, Sm, Gd, Dy, Eu, Er, Yb, Pr, and Ho) based oxide superconductor. There,
The oxide superconductor is an RE salt of a carboxylic acid having 3 to 8 carbon atoms not containing a ketone group as an RE component, barium trifluoroacetate as a Ba component, and a branched saturated aliphatic having 6 to 16 carbon atoms as a Cu component. Contains one or more types of copper salts selected from the group consisting of copper salts of carboxylic acids and copper salts of alicyclic carboxylic acids having 6 to 16 carbon atoms, and an organic solvent for dissolving these metal salt components as essential components To
Oxide superconducting wire. The RE component comprises an yttrium salt;
The oxide superconducting wire according to claim 1. The RE component is a propionate containing no fluorine atom,
The oxide superconducting wire according to claim 5 or 6. The said solution is apply | coated to the surface of the said base material by pulling up a tape-shaped base material from the container in which the solution of the composition for oxide superconductors of any one of Claim 1 to 4 was accommodated. Application process;
A calcining heat treatment step of subjecting the applied solution to a calcining baking treatment to form a precursor of an oxide superconductor on the surface of the substrate;
The precursor is subjected to a main baking heat treatment to be crystallized, whereby REBaCuO (RE is a group consisting of Y, Nd, Sm, Gd, Dy, Eu, Er, Yb, Pr, and Ho is formed on the surface of the base material. A main baking heat treatment step of forming an oxide superconductor of at least one element selected from:
The manufacturing method of the oxide superconducting wire which has this. The application step and the pre-baking heat treatment step are repeated 1 to 10 times to form the precursor,
The manufacturing method of the oxide superconducting wire of Claim 8.

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